1S99J PatTKn.— Nest of Little Tern. 193 



mostly into requisition ? Some observers think the feet are 

 mainly used. But here a difficulty presents itself in this 

 theory. 



The finished excavation is on an average 5 cm. (2 inches) 

 in depth, whereas the foot (tarso-metatarsus) of the Little Tern 

 measures only 2 cm. + 1 mm. (| inch nearly) in length. It 

 is difficult to understand how the bird could balance itself and 

 at the same time dig a hole, conical in shape, the depth of 

 which is to be more than twice the length of its feet. The 

 beak, head, and neck, would be very much in the way, and 

 the sand could never be thrown up on the surface. 



I am strongly inclined to agree with Mr. Williams, and to 

 believe that the process of excavating is performed mainly, if 

 not in toto, by the beak. 



This structure is admirably adapted for the purpose. Being 

 relatively long (4 cm. or if inches), wedge-shaped, and 

 strongly made, it can be used after the fashion of a pick-axe, 

 until the requisite depth is reached. If at the same time that 

 the beak was at work, the bird walked round a circle the 

 centre of which is at its beak and the distance an imaginary 

 radius from its beak to its feet, the tendency obviously would 

 be for the depression to assume ultimately a conical form. 

 This would be more or less pronounced according to the 

 alterations in the oblique direction of the beak. So much for 

 the description of the unfinished nest. 



When completed and containing the full clutch of two or 

 three eggs we note that the deepest and narrowest part of the 

 nest is now filled up with broken shells, which for the 

 purpose of description wc may term " lining shells" (fig. 2, 1). 



Some of these, especially the larger pieces, are pressed 

 against the upper part of the shelving wall, and may even 

 reach to the surface. 



Immediately surrounding the nest is a " zone" or " girdle " 

 of comparatively bare sand from which the shingles have been 

 removed save a few of the larger and more entire examples. 

 Outside the " zone " shingles are scattered plentifully. 



A rough diagrammatic sketch of the completed nest, as seen 

 in vertical section (containing the three eggs), will serve to 

 illustrate these remarks, and to make them clearly understood. 

 (fig. 2). 



